The individual nerve cells in the somatosensory thalamus (VPL, VPM) are arranged in a precise manner, according to the peripheral locations of their receptive fields. There is evidence to indicate that the arrangement of these cells also depends on the modality characteristics of the receptive fields. The objective of this project is to gain an understanding of the organization of the somatosensory thalamus by using mecroelectrodes to record from single thalamic neurons in macaques in the absence of general anesthesia, determining the location and extent of the receptive field of each neuron, using quantitative tactile stimuli (brush strokes, skin indentation) to specify their submodality characteristics, and finally determining the precise location of each neuron studied by the use of histological techniques. It is hoped that the principles of organization revealed by the study will lead to a new understanding of the function of the thalamic component of the somatosensory system. BIBLIOGRAPHIC REFERENCES: Loe, P. R., Dreyer, D. A., Metz, C. B., Rustioni, A., and Whitsel, B. L. Thalamocortical projections and body representation in the ventroposterior nucleus of the macaque thalamus. Neuroscience Abstracts 1: 126, 1975.